1. Field of the Invention
The present invention relates to the refrigerating apparatus used in a refrigerated showcase, a refrigerator, an air conditioner, or the like.
2. Description of the Prior Art
This type of conventional refrigerating apparatuses such as the device for air conditioners disclosed in Japanese Utility Model Publication No. (sho) 61-2447 (F25B 1/00), comprise a compressor, a condenser, an expansion device, and an evaporator, serially connected by piping to form a closed loop. The apparatus condenses the refrigerant discharged from the compressor in the condenser, expands it in the expansion device, and introduces it into the evaporator where it evaporates, thereby cooling the interior of a refrigerated showcase, for example.
FIG. 8 illustrates the refrigerant circuit of the refrigerating apparatus 100 of a conventional refrigerated showcase. FIG. 8 shows a rotary type compressor 1, a condenser 2 connected by piping to the discharge side 1D of the compressor 1, and a solenoid valve 3 connected to the outlet side of the condenser 2. FIG. 8 further shows a capillary tube 4, which is used as an expansion device, connected to the outlet side of the solenoid valve 3, an evaporator 6 connected to the outlet side of the capillary tube 4, and a check valve 7 connected by piping between the outlet side of the evaporator 6 and the suction inlet side 1S of the compressor 1. The positive direction of the check valve 7 is the same as the operating direction of the compressor 1.
In the above construction, when the interior temperature of a refrigerated showcase (not shown) rises to the preset upper limit, a control device which includes a thermostat (not shown) starts the compressor 1. The solenoid valve 3 is opened simultaneously with the start of the compressor 1. Then the gas refrigerant which is under high pressure and temperature is discharged from the discharge side 1D of the compressor 1 and flows into the condenser 2 where the gas refrigerant loses its heat and condenses into liquid. The liquid refrigerant from the outlet of the condenser 2 flows through the solenoid valve 3 and through the capillary tube 4, where its pressure is lowered, and finally flows into the evaporator 6. The refrigerant introduced into the evaporator 6 evaporates and cools the air surrounding the evaporator by taking heat away from its immediate surroundings. The gas refrigerant from the outlet of the evaporator 6 flows through the check valve 7 and is sucked into the compressor 1 at the suction side 1S of the compressor 1.
The cooled air refrigerated in the evaporator 6 is circulated to the interior of the refrigerated showcase and thereby refrigerates it. When the interior temperature falls to the preset lower limit of such refrigerating operation, the control device stops the compressor 1 and simultaneously closes the solenoid valve 3 to stop the refrigerating operation.
When the compressor 1 stops, the flow of the liquid refrigerant from the condenser 2 through the capillary tube 4 to the evaporator 6 is prevented by this closing of the solenoid valve 3. The refrigerant is prevented from flowing back from the suction side 1S of the rotary type compressor 1 to the evaporator 6 by the check valve 7. Thus, the pressure difference between the high pressure side and the low pressure side remains when the compressor 1 stops.
Recently, reducing the noise generated by the compressor in such refrigerated showcases has become a problem as the standard of living improves. Noise reduction is especially important for showcases used in shops integrated with houses.
In the conventional refrigerating device 100, the pressure difference between the high pressure side and the low pressure side remains when the compressor stops. Since the refrigerant remains in the evaporator 6, the pressure of the refrigerant rises when the compressor 1 is not running. The pressure at the suction side 1S of the compressor is thus high when the compressor is started again. In the conventional refrigerating apparatus, the high pressure at the suction side 1S of the compressor 1 increases the required torque needed to start the compressor and thereby creates excessive loads on the bearings, and causing a relatively loud noise similar to the sound of a buzzer for a relatively long time period from t1 (start) to t2, as shown in FIG. 9.